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IMMOBILISER SYSTEM, Diagnostic DTC:B278A

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DTC Code DTC Name
B278A Short to GND in Immobiliser System Power Source Circuit
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DESCRIPTION

When there is a short to GND in the power supply for the transponder key amplifier of the engine switch, the certification ECU (smart key ECU assembly) stores this DTC.

DTC No. Detection Item DTC Detection Condition Trouble Area Note
B278A Short to GND in Immobiliser System Power Source Circuit A short to GND in the power supply of the transponder key amplifier of the engine switch (VC5 - VC5) detected. (1 trip detection logic*)

  • Engine switch

  • Certification ECU (smart key ECU assembly)

  • Wire harness or connector

DTC output confirmation operation:


  • With the shift lever in P and the key held near the engine switch, an engine start operation is performed by pressing and holding the engine switch when the transmitter battery is depleted.

Table 1. Vehicle Condition and Fail-safe Operation when Malfunction Detected
Vehicle Condition when Malfunction Detected Fail-safe Operation when Malfunction Detected
Engine cannot be started when transmitter battery is depleted by holding transmitter near engine switch and pressing and holding engine switch with shift lever in P -
Table 2. Related Data List and Active Test
DTC No. Data List and Active Test
B278A -
Table 3. *1 Engine Switch *2 Certification ECU (Smart Key ECU Assembly)
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WIRING DIAGRAM

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CAUTION / NOTICE / HINT

Note:

  • When using the GTS with the engine switch off, connect the GTS to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the GTS and the vehicle begins. Then select Model Code "KEY REGIST" under manual mode and enter the following menus: Body Electrical / Entry&Start(CAN). While using the GTS, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the GTS and the vehicle.

  • Before replacing the certification ECU (smart key ECU assembly), refer to Service Bulletin.

  • After repair, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

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PROCEDURE


  1. Click here

    CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. B0066U0C25
      *a

      Component with harness connected

      (Engine Switch)

      		 - -

      Using an oscilloscope, check the waveform.

      Tip:

      Perform this inspection on the engine switch side.

      Measurement Condition
      Tester Connection Condition Tool Setting Specified Condition
      O49-10 (VC5) - O49-6 (AGND) Engine switch off, electrical key transmitter sub-assembly not in cabin, within 30 seconds of engine switch pressed 2 V/DIV., 200 ms./DIV. Pulse generation
      OK
      The waveform is similar to that shown in the illustration.
      Result
      Proceed to
      OK
      NG

  2. Click here

    CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - ENGINE SWITCH)


    1. Disconnect the O6 certification ECU (smart key ECU assembly) connector.

    2. Disconnect the O49 engine switch connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      O6-15 (VC5) - O49-10 (VC5) Always Below 1 Ω
      O6-12 (AGND) - O49-6 (AGND) Always Below 1 Ω
      O6-15 (VC5) or O49-10 (VC5) - Body ground Always 10 kΩ or higher
      O6-12 (AGND) or O49-6 (AGND) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    • OKClick here
    • NG

      REPAIR OR REPLACE HARNESS OR CONNECTOR

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    CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)


    1. Reconnect the O6 certification ECU (smart key ECU assembly) connector.

    2. Reconnect the O49 engine switch connector.

    3. B0065G4C29
      *a

      Component with harness connected

      (Certification ECU (Smart Key ECU Assembly))

      		 - -

      Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      O6-15 (VC5) - O6-12 (AGND) Engine switch off, brake pedal not depressed, 30 seconds or more elapsed since driver door opened and then closed Below 1 V
      Result
      Proceed to
      OK
      NG

    • OK

      REPLACE ENGINE SWITCHClick here

    • NG

      REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)